A known nozzle plate (German Patent No. DE 43 28 418 A1) has a holder plate with a stepped through-bore, where the segment of this bore which lies towards the supply side, and has a smaller diameter, forms the supply opening. An injection plate is inserted into the bore segment with the larger diameter, which plate has a recess in its edge region assigned to the exit side, forming a ring channel together with a recess in the holder plate assigned to it, which channel is connected with the supply opening via slits provided in the side of the injection plate facing the supply opening. The exit-side edges of the recesses in the holder plate and the injection plate delimit a ring-shaped exit opening of the known nozzle plate.
The German patent application P 44 04 021.0 describes another nozzle plate, composed of two parts, in which a ring channel is provided between the two parts, which channel is connected with a fuel supply region via supply bores provided in the first part, and connected with a fuel exit region via a ring gap. The ring gap, in this connection, is delimited by two mantle surfaces in the shape of truncated cones, with the one being attached to the first part of the nozzle plate and the other to the second part.
The two parts of this nozzle plate are produced by galvanic second-casting of corresponding negative molds, consisting of conductive plastic, where the galvanically cast parts can be mechanically finished and subsequently attached to each other by means of gluing, diffusion soldering, or diffusion welding.
Such nozzle plates with ring gap nozzles are used in fuel injection valves for gasoline engines in order to achieve better atomization of the fuel. In this connection, the fuel is supposed to exit as a cohesive laminar jet in the shape of a conical mantle. Because of the radial expanse along the conical mantle, the fuel film becomes thinner with an increasing diameter towards the exit, until it bursts into very small droplets due to aerodynamic forces. In this manner, it is possible to achieve distribution of the fuel over a relatively large volume.
In order to obtain a uniform laminar jet, both uniform pressure distribution and a uniform fuel supply are necessary at the ring gap.